JP5995364B2 - Alkyl zinc halide zinc oxide precursor and zinc oxide thin film deposition method using the same - Google Patents

Description

  The present invention relates to an alkylzinc halide zinc oxide precursor for vapor deposition of a zinc oxide thin film and a method for vapor deposition of a zinc oxide thin film using the same.

  Flat panel displays such as TFT-LCDs, PDPs, FEDs, OLEDs, etc .; solar cells using photoelectric effects; touch screens; etc. require conductive materials that do not block light, that is, transparent conducting electrodes Is done.

The most frequently used material for the transparent conductive film is an indium oxide film (In ₂ O ₃ ) doped with tin (Sn), that is, an indium tin oxide film (ITO, Indium Tin Oxide). Indium tin oxide film (ITO) has excellent electrical conductivity because of its low specific resistivity (about 1-2 × 10 ⁻⁴ Ωm), high transmittance in the visible light region, and excellent chemical stability. Therefore, it is widely used as a transparent electrode material. However, indium (In), which is a main constituent element of an indium tin oxide film, has an extremely small reserve amount compared to tin (Sn), zinc (Zn), and the like, so that the price is as high as that of silver (Ag). In addition to this, there is a problem that prices fluctuate rapidly. For this reason, research on materials that can replace indium is being actively pursued.

  In recent years, materials that have been studied extensively as alternative materials for indium tin oxide films (ITO) are cations such as zinc oxide (ZnO), aluminum (Al), gallium (Ga), indium (In), and boron (B). It is a material doped with an elemental group 3 metal element or a halogen element such as fluorine (F).

  A zinc oxide-based thin film can be deposited on a substrate by a physical vapor deposition method. When a sputtering process is used in the physical vapor deposition method, a zinc oxide (ZnO) -based target material is used. A target is used (Korea published patent number: 10-2008-0064269).

  Further, the zinc oxide-based thin film can be deposited on the substrate by a chemical vapor deposition method. Conventionally, DEZ (Dietyl zinc), DEZ octane solution, etc. have been used as a raw material. (Korea published patent numbers: 10-2007-0053617, 10-2006-0125500).

  FIG. 1 is a diagram schematically showing a conventional PECVD apparatus for depositing a zinc oxide-based thin film using DEZ or DMZ as a raw material.

The figure illustrates a PECVD apparatus for depositing undoped ZnO and F- and B-doped ZnO. The PECVD apparatus in FIG. 1 introduces a reaction composition by introducing DEZ or DMZ as a volatile organometallic zinc compound; Ar or He as a carrier gas; CO ₂ as an oxidizing agent; and triethylboron or nitrogen trifluoride as a doping agent. Then, the reaction composition is introduced into the vapor deposition chamber 1 to deposit a zinc oxide thin film on the substrate 5.

  Unexplained reference numeral 2 is an upper electrode, 3 is a lower electrode, 4 is a hole, 6 is an opening, 7 is a power source, 8, 9, 10, 11, 12, and 13 are lines, 14, 15, 16, 17 , 18 and 19 are flow control devices, and 20 is a heat holding device.

  FIG. 2 is a view schematically showing a conventional deposition chamber in which a zinc oxide-based thin film is deposited using a solution prepared by dissolving DEZ in an organic solvent as a raw material.

  A solution prepared by dissolving DMZ (dimethylzinc) or DEZ (diethylzinc) in an organic solvent (ether, ketone, ester, hydrocarbon or alcohol) is vaporized and supplied to the CVD apparatus via the supply pipe 24, and at the same time Oxidant gas (oxygen gas, ozone gas, nitrogen oxide gas or vapor) is supplied to the deposition chamber through the supply pipe 25.

  Unexplained reference numeral 21 denotes a substrate, 22 denotes a susceptor, 23 denotes a heater, 26 denotes a rotating shaft, 27 denotes a reaction gas discharge unit, and 29 denotes a reaction chamber.

  However, as shown in FIG. 1, when DEZ or DMZ is used, there is a problem that the vapor pressure is too high, the risk of ignition due to high reactivity is high, and the composition control of the thin film is not easy. In particular, due to the high flammability risk due to high reactivity, the deposition of zinc oxide thin films using precursors such as DEZ and DMZ must be performed under low pressure, and atmospheric pressure chemical vapor deposition cannot be used. There is a bug.

  In addition, as shown in FIG. 2, the method of diluting a precursor such as DEZ or DMZ in an organic solvent has an advantage that spontaneous ignition can be suppressed, but low deposition due to low zinc content. There is a problem that the yield is low depending on the speed. Further, since the flammability is increased by a solvent that is not volatilized at the time of low temperature vapor deposition, there is a disadvantage that it can be used only at high temperature vapor deposition.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to synthesize an alkyl zinc halide, which is an organic compound that can replace conventional DEZ or DMZ, and to chemistry the zinc oxide thin film. It is to be applicable to phase deposition.

  In the chemical vapor deposition process of thin films, it improves the process problems due to thermal and chemical instability, has excellent thermal and chemical stability and high vapor pressure, and does not ignite moisture and air The purpose is to deposit a pure zinc oxide-based thin film free of impurities such as carbon by providing new raw materials and changing only process conditions such as reaction gas and deposition temperature.

  In particular, it is an object of the present invention to enable mass production of a zinc oxide-based thin film by atmospheric pressure vapor deposition suitable for a mass production process due to a high deposition rate and high productivity.

In order to achieve the above object, the present invention provides a precursor for use in vapor deposition of a zinc oxide-based thin film, which is an alkylzinc halide represented by the following chemical formula: I will provide a.

In the above formula, R represents an alkyl group (C _n H _{2n + 1} ), and X represents a halogen group.

  Preferably, n of the alkyl group is 1 to 4, and more preferably, the alkyl group includes a methyl group, an ethyl group, an i-propyl group, or a t-butyl group.

  Preferably, the halogen group includes F, Br, Cl, or I.

  The present invention also includes a step of disposing a substrate in a vapor deposition chamber, a step of supplying the alkylzinc halide zinc oxide precursor and an oxidizing agent to the vapor deposition chamber, and performing chemical vapor deposition of a zinc oxide-based thin film on the substrate. And a method for vapor-depositing a zinc oxide-based thin film.

  Preferably, the zinc oxide thin film is deposited on the substrate by atmospheric pressure chemical vapor deposition.

  According to the above configuration, the alkylzinc halide organometallic compound according to the present invention has a flammability of a by-product generated in the reaction with an oxidant from the flammability of ethane gas or methane gas, which is a precursor oxidation by-product of DEZ or DMZ. Therefore, it can be applied to atmospheric pressure chemical vapor deposition relatively safely.

  Due to the low flammability, there is no need to dilute in hydrocarbon solvents, so high yields can be obtained with high deposition rates with high zinc content precursors.

It is a figure which shows roughly the conventional PECVD apparatus which vapor-deposits a zinc oxide type thin film using DEZ or DMZ as a raw material. It is a figure which shows roughly the other conventional vapor deposition chamber which vapor-deposits a zinc oxide type thin film using the solution manufactured by melt | dissolving DEZ in the organic solvent as a raw material. It is a figure which shows the various alkyl zinc halides of this invention. It is a figure which shows the result of having analyzed the ethyl zinc chloride manufactured according to one Embodiment of this invention. It is a figure showing roughly the CVD device concerning one embodiment of the present invention. It is a figure which shows roughly an example of the canister of FIG. It is a figure which shows roughly an example of the canister of FIG. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 1st Embodiment. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 1st Embodiment. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 1st Embodiment. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 2nd Embodiment. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 2nd Embodiment. It is a figure which shows the analysis result of the zinc oxide type thin film vapor-deposited according to 2nd Embodiment.

In the present invention, as an organometallic compound that can be used in place of a zinc oxide precursor such as DEZ and DMZ that has been used, chemical vapor deposition (Chemical Vapor) using an alkyl zinc halide represented by Chemical Formula 1 is used. (Deposition, CVD).

In the above formula, R represents an alkyl group (C _n H _{2n + 1} ), and X represents a halogen group.

  In this case, n is preferably 1 to 4, and for example, R is any one of a methyl group, an ethyl group, an i-propyl group, and a t-butyl group. X is preferably any one of F, Br, Cl, and I. FIG. 3 shows various alkyl zinc halides of the present invention having the alkyl group and the halogen group.

  When the alkylzinc halide represented by the chemical formula 1 is used as a raw material, it is not necessary to dilute the hydrocarbon solvent with the low reactivity and flammability of the raw material with respect to DEZ. Can be obtained. In addition, since the flammability of the by-product generated in the reaction with the oxidant is lower than the flammability of ethane gas, methane gas, etc., which are precursor oxidation by-products such as DEZ and DMZ, chemical vapor deposition (Chemical vapor deposition) Zinc oxide thin films can be deposited by applying to Vapor Deposition (CVD).

  Among the compounds represented by the chemical formula 1, the compound in which R has a methyl group or an ethyl group has a high vapor pressure, so that it is easy to supply the precursor and control the flow rate, and at a low temperature. There is an advantage that it can be deposited under process conditions. In particular, methylzinc chloride (boiling point: 67 ° C.) and ethyl zinc chloride (boiling point: 215 ° C.) in FIG. 4 are more preferably used as raw materials for chemical vapor deposition.

  After producing zinc halide as a dispersion solution in an inert gas atmosphere using an organic solvent, dialkylzinc diluted in the organic solvent is added to cause a redistribution reaction, thereby producing an alkyl zinc halide. can do. Moreover, after producing a dispersion solution of zinc halide using an organic solvent, an alkyl zinc halide can be produced by adding an alkali metal or an alkaline earth metal to cause a substitution reaction.

  FIG. 5 is a diagram showing a schematic structure of a CVD apparatus according to an embodiment of the present invention.

  The CVD apparatus may include a canister 113 with a dip tube as shown in FIG. 6 or a tube as shown in FIG. 7, or a vaporizer to vaporize the alkyl zinc halide. i) A gas is supplied from the gas supply unit 111 to the canister 113 through a dip tube or a tube to help vaporize the alkyl zinc halide, or ii) a gas state obtained by generating only steam without supplying the gas. Alkyl zinc halide is supplied together with a carrier gas.

  At this time, an oxidant gas (oxygen gas, ozone gas, nitrogen oxide gas, water vapor, or alcohol vapor) is supplied to the vapor deposition chamber 101 from the oxidant supply units 115 and 117.

  The upper electrode 102 has the form of a shower head. A showerhead refers to a chamber, plenum, or other structure having a plurality of openings through which precursors and the like are discharged into the deposition chamber 101.

  The substrate 105 may be a silicon substrate, a sapphire substrate, a ceramic substrate, a glass substrate, a metal oxide substrate, a metal substrate, or the like. In order to efficiently form the zinc oxide-based thin film, the temperature of the substrate may be set to 100 to 400 ° C, and preferably set to 250 to 350 ° C. A reproducible zinc oxide thin film can be formed by chemical vapor deposition of the supplied organozinc compound on a substrate heated at the temperature.

  In order to obtain a zinc oxide-based thin film doped with a dopant (eg, gallium), a doping agent may be introduced into the deposition chamber 101 and deposited together, or a doping process may be performed as a subsequent process. .

(First embodiment)
After setting the glass substrate in the heating part of the vapor deposition chamber of the CVD apparatus and setting the degree of vacuum in the vapor deposition chamber to 1.0 × 10 ⁻⁶ torr, the temperature inside the canister is set to 50 ° C. and the temperature of the substrate Was kept at 300 ° C. The gas flow controller supplies gas to the ethyl zinc chloride precursor at a flow rate of 20 sccm / min to help vaporize the raw material, and argon gas is supplied at 50 sccm / min through a carrier gas supply line heated to 80 ° C. A zinc oxide thin film was formed on the glass substrate for several minutes by supplying oxygen gas at a flow rate of 13 sccm / min.

As a result of analyzing the thus obtained zinc oxide-based thin film with a scanning electron microscope, crystallinity grown in the c-axis direction having a cylindrical structure with a thin film thickness of 344 nm was shown (FIGS. 8 and 9). Further, as a result of X-ray diffraction analysis, a (002) crystal plane in the c-axis direction was shown in the vicinity of a 2θ (degrees) value of 34.4 (FIG. 10). Moreover, as a result of analyzing with a surface resistance measuring device, 6.686 × 10 ¹ Ω / sq (specific resistance 2.3 × 10 ⁻⁴ ΩCm) was shown. Moreover, as a result of analyzing with an infrared spectroscopic analyzer, it was shown to have a transmittance of 80% or more in the visible light region.

    As a result, it was possible to obtain a transparent conductive zinc oxide-based thin film having a (002) crystal plane in the c-axis direction that is excellent in terms of carrier mobility and having high light transmittance and low resistance.

(Second Embodiment)
After setting the glass substrate in the heating part of the CVD apparatus and setting the CVD apparatus to normal pressure, the temperature inside the canister was set to 50 ° C., and the temperature of the substrate was maintained at 350 ° C. The gas flow controller supplies gas to the ethyl zinc chloride precursor at a flow rate of 500 sccm / min to help vaporize the raw material, and argon gas is supplied at 200 sccm / min via a carrier gas supply line heated to 80 ° C. The zinc oxide thin film was formed on the glass substrate for several minutes by supplying oxygen gas at a flow rate of 130 sccm / min.

As a result of analyzing the obtained zinc oxide thin film with a scanning electron microscope, the crystallinity grown in the c-axis direction having a columnar structure with a thin film thickness of 875 nm was shown (FIGS. 11 and 12). Further, as a result of X-ray diffraction analysis, a (002) crystal plane in the c-axis direction was shown in the vicinity of a 2θ (degrees) value of 34.4 (FIG. 13). Moreover, as a result of analyzing with a surface resistance measuring device, 8.0 × 10 ¹ Ω / sq (specific resistance 7 × 10 ⁻⁴ ΩCm) was shown. Moreover, as a result of analyzing with an infrared spectroscopic analyzer, it was shown to have a transmittance of 80% or more in the visible light region.

    As a result, it was possible to obtain a transparent conductive zinc oxide-based thin film having a (002) crystal plane in the c-axis direction that is excellent in terms of carrier mobility and having high light transmittance and low resistance.

101: Deposition chamber 102: Upper electrode 103: Lower electrode 105: Substrate 111: Carrier gas supply unit 113: Canister 115, 117: Oxidant supply unit

Claims (7)

A precursor used in the deposition of the zinc oxide based thin film, wherein the to luer alkyl zinc halides zinc oxide precursor an alkyl zinc halide represented by the following chemical formula.
(Wherein, R represents an alkyl group (Cn H2n + 1), X is table a halogen group, the alkyl group is a methyl or ethyl group, the halogen group is Cl.) A alkyl zinc halides zinc oxide precursor of claim 1, wherein the zinc oxide precursor atmospheric pressure chemical vapor for deposition. Placing a substrate in a deposition chamber;
Comprising the steps of claim 1 or 2 A alkyl zinc halides zinc oxide precursor and an oxidizing agent according to supplied to the deposition chamber, to chemical vapor deposition of zinc oxide based thin film on a substrate,
A method for depositing a zinc oxide-based thin film, comprising: 4. The method for depositing a zinc oxide-based thin film according to claim 3 , wherein the zinc oxide-based thin film is deposited on the substrate by atmospheric pressure chemical vapor deposition. After vaporizing before Kia alkyl zinc halides zinc oxide precursor, the method of deposition zinc oxide-based thin film according to claim 3 or 4, characterized in that supplied to the deposition chamber in a gas state. The zinc oxide-based thin film according to any one of claims 3 to 5 , wherein the oxidizing agent is at least one of oxygen gas, ozone gas, nitrogen oxide gas, water vapor, and alcohol vapor. Deposition method. The zinc oxide thin film deposition according to any one of claims 3 to 6 , wherein the substrate is a silicon substrate, a sapphire substrate, a ceramic substrate, a glass substrate, a metal oxide substrate, or a metal substrate. Method.